The present invention relates to disposable valves and more particularly to an actuator controlled diaphragm valve having a valve insert made out of a moldable plastic having a fluid chamber and a diaphragm component capable of controlled, repeatable and accurate dispensing of fluid materials of various types and viscosities and in various forms, such as beads, dots and the like.
Positive displacement rotary microvalves are known for dispensing fluid materials such as adhesives, epoxies, potting compounds, SMT adhesives, two-part adhesives, silver and gold filled adhesives, UV curable adhesives, and solder pastes in a repeatable and accurate manner. Typically, these dispensers for fluid material are used in a wide variety of industries, such as electronic assembly and repair, form in place gasketing, component assembly and sealing, mold-making, casting, tool and machine and equipment fabrication and assembly, and a variety of other uses.
Prior dispensing devices typically include a gear motor which controls the rotation of a feed screw supported in a housing. Fluid is fed to the housing from an external pressure on the fluid and to force the fluid material into the housing. Supported in the housing for rotation by the motor is a feed screw or auger which urges the fluid material into a dispensing tip which is affixed to the output end of the housing. The dispensing tip is essentially in the form of a pointless needle which is locked and sealed to the output end of the housing.
The valve includes a rotary screw of a variable pitch type which homogenizes low viscosity material and which compresses the material to reduce its volume. A one piece housing having a sleeve located in the bore and which extends only partly up the bore area. The housing also includes a passageway formed in the housing through which the fluid flows and which is in contact with the passage wall as the fluid is urged into the bore. The portion of the bore above the sleeve may be contacted with the fluid since there is no seal between the upper portion of the bore and the sleeve. The housing also includes a screw which holds a dispensing coupling and thus the sleeve and the bore, a gasket being provided between the dispensing coupling and the lower portion of the sleeve.
Although prior microvalve dispensers operate satisfactorily, there are circumstances which require improvements which can be made. For example, dispensers are normally used continuously in assembly line and commercial operations except during lunch breaks and after a shift is over. If the material being dispensed hardens in the microvalve or degrades for any reason, then the valve has to be cleaned out and this is a difficult operation. Should such hardening occur, the unit is often sent back to the supplier for cleaning and thus may be expensive and create considerable down time. In addition, materials being dispensed may change during operation and it may be the case that later dispensed material is contaminated by that previously dispensed or is incompatible with the previously dispensed material. In such a case, the contamination must be cleaned out of the valve, which also can lead to considerable expense and down time for cleaning.
Consequently, improvements to address these issues were developed such that all interior surfaces that come into contact with fluid being dispensed were readily replaceable therefore reducing costs of cleaning and repair and reducing down time in assembly and commercial operations. Such microvalve devices included a conventional gear driven motor unit to which was mounted a housing for the valve. Supported within the housing was a disposable insert chamber which forms the interior wet surfaces of the dispenser. The insert includes a feed arm through which fluid under pressure from an external source is fed to the interior of the insert and thus the fluid does not contact the feed arm surfaces of the housing of the microvalve. Located in the insert is a feed mechanism connected to and driven by the motor, to dispense a measured amount of fluid accurately and controlled by the motor. Such prior disposable inserts required a motor having and output shaft for driving a helical screw or auger supported for rotation in the insert. Fluid in a measured amount, depending on the rotational speed and configuration of the screw was urged out of the outlet which forms the exit passageway for the insert. Although such disposable rotary microvalve insert configuration works well, having to include a helical screw or auger supported for rotation within the insert is a complicated mechanism adding to the complexity and expense of the insert which is disposable. Consequently a need exists for a simplified disposable valve insert which is less expensive to manufacture yet provides consistent and reliable performance.